Part2 - spawn

launch gazebo and spawn entity

#gazebo-classic   #tutorial   #spawn  

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Table of Content

project

my ros2_gazebo_tutorial

├── CMakeLists.txt
├── launch
│   └── spawn.launch.py
├── package.xml
├── worlds
│   └── empty.world
└── models
    └── simple
        ├── model.config
        └── model.sdf.xacro

launch

basic_gazebo.launch.py

import os

from ament_index_python import get_package_share_directory
from launch import LaunchDescription
from launch.actions import IncludeLaunchDescription, AppendEnvironmentVariable, DeclareLaunchArgument
from launch.substitutions import LaunchConfiguration
from launch.launch_description_sources import PythonLaunchDescriptionSource
from launch_ros.actions import Node
import xacro

PACKAGE = "ros2_gazebo_tutorial"
WORLD = "camera.world"
MODEL = "camera2"
SDF = "model.sdf"


def generate_launch_description():
    gazebo_pkg = get_package_share_directory("gazebo_ros")
    pkg = get_package_share_directory(PACKAGE)

    verbose = LaunchConfiguration("verbose")
    arg_gazebo_verbose = DeclareLaunchArgument("verbose", default_value="true")
    world = LaunchConfiguration("world")
    arg_gazebo_world = DeclareLaunchArgument("world", default_value=WORLD)
    sim_time = LaunchConfiguration("sim_time")
    arg_sim_time = DeclareLaunchArgument("sim_time", default_value="true")

    resources = [os.path.join(pkg, "worlds")]

    resource_env = AppendEnvironmentVariable(
        name="GAZEBO_RESOURCE_PATH", value=":".join(resources)
    )

    models = [os.path.join(pkg, "models")]

    models_env = AppendEnvironmentVariable(
        name="GAZEBO_MODEL_PATH", value=":".join(models)
    )

    gazebo = IncludeLaunchDescription(
                PythonLaunchDescriptionSource([os.path.join(
                    gazebo_pkg, 'launch', 'gazebo.launch.py')]),
                    launch_arguments={'verbose': verbose, "world": world}.items()
             )

    robot_description_path = os.path.join(pkg, "models", MODEL, SDF)
    doc = xacro.parse(open(robot_description_path))
    xacro.process_doc(doc)

    robot_state_publisher = Node(
        package='robot_state_publisher',
        executable='robot_state_publisher',
        parameters=[
            {
                'use_sim_time': sim_time, 
                'robot_description': doc.toxml()
            }
        ]
    )

    spawn_entity = Node(
        package="gazebo_ros",
        executable="spawn_entity.py",
        arguments=["-entity", "demo", "-topic", "robot_description"],
        output="screen",
    )

    tf = Node(
            package="tf2_ros",
            executable="static_transform_publisher",
            output="screen",
            arguments=["0","0","0.5","0","0","0","world","link"]
        )

    ld = LaunchDescription()
    ld.add_action(arg_gazebo_verbose)
    ld.add_action(arg_gazebo_world)
    ld.add_action(arg_sim_time)
    ld.add_action(resource_env)
    ld.add_action(models_env)
    ld.add_action(robot_state_publisher)
    ld.add_action(tf)
    ld.add_action(gazebo)
    ld.add_action(spawn_entity)
    return ld